Patent GB-1156451-A (GB)
Title: A Hydraulic Control System for Selecting Forward and Reverse Transmission and for Steering an Endless Track Vehicle through its Tracks
Inventor: ZISKAL JOSEPH FRANCIS
IPC: B62D11/08
Filed: 1965-04-26
Abstract: 1,156,451. Declutching and braking for steering. INTERNATIONAL HARVESTER CO. OF GREAT BRITAIN Ltd. 25 July, 1966 [26 April, 1965], No. 17482/65. Heading B7H. [Also in Division F2] A control system for operating forward and reverse transmission clutches and a steering clutch and brake for each track of an endless track tractor, the transmission clutches being interposed between an engine and a main gear-box and the steering clutches and brakes being incorporated between the main gear-box and the vehicle tracks and being individually or collectively operable, comprises a selector control means for the transmission and additional control means for the steering clutches and brakes, the two control means being interlocked so that the steering clutches and brakes cannot be operated until either the forward or reverse transmission clutch has been engaged. The tractor transmission 68, Fig. 6, has an input shaft 67 which may be connected to an engine drive shaft 66 by a clutch 47 for forward drive and an input shaft 72 which may be connected to the engine shaft 66 through gears 69, 70, 71 and a clutch 48 for rearward drive. A transmission brake 75 is located on the shaft 72. The final drive includes a pair of bevels 80, 81, the latter being mounted on a hollow transverse shaft 82 at each end of which is located an epicyclic gear arrangement comprising a ring gear 83, planets 85 mounted on a cage 84 and a sun-wheel 86 fixed upon a shaft 87 to which is connected a band brake 88. The action of each brake 88 is effectively that of a clutch and applies drive to the respective track. The planet cage 84 is fixed upon a shaft 89 upon which is mounted a band brake 96 and which drives the track drive sprocket 94 through pinions 91, 92 and shaft 93. If neither brake 88 or 90 is applied, the input gear 81 rotates idly. If brake 88 is applied, the track drive sprocket is driven through the planets and planet cage. If brake 90 is applied, the track drive sprockets are locked. An hydraulic control system for the forward and reverse clutches 47, 48, transmission brake 75, and the joint or separate control of the brakes 88 and 90 associated with each track for unsteered or steered movements, Fig. 1, is supplied with oil from the engine sump 4 through a filter 2 by a pump 1. The output line 5 supplies lines 6 and 8 in parallel with a line 7 to a pressure control valve 9 which delivers low pressure oil through a line 18 and has a line 14 connected to reservoir. The line 6 supplies a pair of sliding spool valves 11 in parallel which may be jointly or separately operated for actuating cylinders 45 and 46 for applying the brakes 90 and 88, respectively, on each side of the vehicle. The line 8 supplies a rotary valve 17 which has output lines 19, 20 and 21 for actuating the clutch 47, a cylinder 26 for applying the transmission brake 75 and the clutch 48 such that in moving from the position in which one clutch is applied to the position for applying the other, the transmission brake must be applied. The line 18 supplies oil at a low-pressure to the body of valve 17 for lubrication purposes. The valves 7, 17, 11 and 11 are banked together in a unit, the spools 28 of valves 11 being operated by levers 108, in side by side relationship, through bell-cranks 110 and the valve 17 by rotation of a lever 112 upon a pivoted shaft 111 through a mechanism 113. The lever 112, which is pivoted at 122 and has a cam surface 114 against which cam surfaces 115 upon the levers 108 are urged by springs 116, operates within a gate 117 of H shape so that it may be moved laterally for engagement of either the forward or reverse clutches 47 or 48 and longitudinally along the stems of the H for the joint (unsteered) action of valves 11 through levers 108. The lever 112 can also be moved to a position wherein the selected clutch 47 or 48 remains engaged and the levers 108 may be separately operated for steering, the release of the brake 88 on one side, in effect de-clutching the drive, giving gradual steering to that side and the application of the brake 90 giving more rapid steering to that side. The clutch arrangement, Fig. 4, comprises an input shaft 66 from the engine, an output shaft 67 for forward transmission, and an output gear 69 for rearward transmission through the shaft 72 upon which is mounted the transmission brake 75. The multiplate clutches 47 and 48 are actuated by members 49 and 50 in response to fluid pressure applied through ports 57 and 62, respectively. The transmission brake 75 comprises a friction band 74 wrapped around the drum 75, being anchored at 76 at one end and connected at the other to a piston 77 working in the cylinder 26 to which fluid pressure is supplied through the line 24. A return spring 78 for releasing the brake is provided. The brakes 88 and 90 are in side by side relationship and each comprises a band 96 wrapped around the drum and connected, respectively, to levers 99 and 100, clockwise movement of which about a fixed pivot 98 caused by the hydraulic cylinders 45 and 46 contract the bands upon the drums. Return springs 105 are provided.